But a tie-up would still have married up some of the best-known and most powerful media brands in the US.

Time Warner owns film titan Warner Brothers, CNN, DC Comics and TV channels including the Cartoon Network and HBO.

Murdoch’s business includes a 39 per cent stake in British Sky Broadcasting, the 20th Century Fox film house and TV channels such as National Geographic.

And between them the two companies own a host of lucrative sports broadcast rights in football, basketball, golf and baseball.

For each one of Time Warner’s shares, 21st Century Fox offered 1.531 of its non-voting shares plus £18.91 in cash.

But Time Warner laid out a series of reasons why it rebuffed the offer, including that the share portion was comprised of non-voting stock.

The Murdoch empire owns 39 per cent of voting shares but the majority of the stock carries no right to cast a vote on company affairs at annual meetings.

This means there is ‘significant risk and uncertainty as to the valuation’ of that stock, Time Warner said.

In a defence of its existing strategy, the group said its plan to create value for investors was ‘superior to any proposal that 21st Century Fox is in a position to offer’.

It also questioned 21st Century Fox’s ability to run a group of the size that such a deal would create.

If the deal is revived, it would create a media behemoth with revenues of £36billion, with savings from the tie-up thought to have been pegged at around £580million.

Much of that would come from redundancies among the nearly 60,000 staff which the two companies employ between them.

The proposal from 21st Century Fox comes as the lines between telecoms, media and technology companies become increasingly blurred, forcing even major players such as Rupert Murdoch to seek safety in numbers.

Time Warner Cable, spun out of Time Warner, is in talks over a merger with Comcast that would combined America’s two largest cable TV firms.

Telecoms giants Sprint and T-Mobile are seeking regulatory clearance for a merger, while pay-TV firm DirecTV and telecoms firm AT&T are also hoping to seal a combination.

The uncertainty fuelled by the changing landscape means Time Warner may now face calls from its investors, some 70 per cent of whom also own 21st Century Fox shares, to talk to its would-be predator.

Google is also rumoured to have made some sort of tie-up proposal to Time Warner.

But when boss Rodney Bewkes was asked recently to comment on rumours of interest from the internet giant or 21st Century Fox, he said: ‘I know nothing about it.’